Natural Toxins in Nectar and Pollen May Poison Bees

It turns out that natural toxins in nectar and pollen can poison insects, which could have some implications for bees. Scientists have discovered that these toxins can affect insect memory, behavior, and reproductive success.

Bee populations are declining across the world. That's why studying potential harmful impacts to these insects is so crucial. In this case, the researchers examined the impact of naturally-occurring toxins in lupin and rhododendron flowers on bees.

The researchers gave bumblebees pollen treated with lupanine, which is a chemical found in lupin plants, at natural concentrations. They found that the bumblebees produced fewer, smaller males. These consequences could potentially be severe where lupins are cultivated and present the major food source for bees at certain times of the year.

Yet this wasn't the only toxic chemical. The scientists found that other chemicals, called diterpenoids, which are found in the nectar of Rhododendron ponticum, can be toxic to honeybees and a wild mining bee species. Surprisingly, though, bumblebees aren't harmed by the compounds.

That said, plant chemicals aren't all bad. They can sometimes improve honeybee memory or be beneficial to insects. That said, it is something to watch out for when placing hives.

"Plant chemicals in nectar and pollent can mediate specialization in pollinators, can drive plant pollinator interactions and can simply be toxic to pollinators where they have been selected for another purpose in the plant, such as defense against herbivores," said Phillip Stevenson, one of the researchers, in a news release.

The findings highly important considerations when it comes to landscape management of wild plants. Rhododendron ponticum is actually an invasive species, and this study demonstrated that the toxins produced by this plant are poisonous to honeybees. This means that when this plant dominates a landscape, bees may be in trouble.

"Plant toxins need to be considered alongside other stressors on pollinators for their potential to impact ecosystems, so the next phase of our research will be to look at the interactive effects of plant chemicals with other stressors such as disease, so that we can determine whether plant chemicals exacerbate or ameliorate the effects of bee diseases," said Stevenson.

The findings will be presented to the joint BES/SFE meeting in the Grand Palais, Lille.

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